Nelson trailed Scott by about 12,600 votes, or 0.15 percent of the more than 8 million ballots cast following an electronic recount.

Under state law, the Florida Department of State must trigger a manual recount if an electronic recount of ballots finds a margin of victory of less than 0.25 percent.

Elections officials were expected to inspect by hand any ballots that were designated undervotes or overvotes, cases where the machine that reviewed the ballot concluded that a voter had skipped a contest or marked more than one selection.

If the voter's intentions are clear on review by a person, the ballot could be counted.

The order came after U.S. District Judge Mark Walker in Tallahassee, Florida, cleared the way to include ballots from as many as 5,000 people across the state who submitted ballots by mail that were rejected by election officials. A Georgia federal judge issued a similar ruling as that state worked to resolve a close governor's race.

In Florida, the recount of close races and attendant legal disputes over the validity of votes have stirred memories of the 2000 U.S. presidential election, when the U.S. Supreme Court stopped an ongoing recount in the state and sent George W. Bush to the White House.

State election officials said the machine recount of ballots in the governor's race pitting Republican Ron DeSantis against Democrat Andrew Gillum showed DeSantis with an 0.41 percentage point lead, below the threshold to trigger a manual recount.

Gillum signaled that he had not yet given up.

"A vote denied is justice denied — the State of Florida must count every legally cast vote," Gillum said in a statement after the machine recount concluded. "We plan to do all we can to ensure that every voice is heard in this process."

The Scott campaign in a statement called on Nelson to concede.

"Last week, Florida voters elected me as their next U.S. Senator and now the ballots have been counted twice," Scott said in a statement.

Overall control of the U.S. Senate is not at stake in the Florida race. President Donald Trump's fellow Republicans extended their majority in the chamber while Democrats took a majority in the House of Representatives. But both the Senate and governor's races are being closely scrutinized as Florida is traditionally a key swing state in presidential elections.

'LAUGHING STOCK'

Walker grew testy during a series of Thursday hearings about lawsuits over the recounts, voicing frustration about how to handle uneven progress in different counties and also the Florida legislature's response to historic election problems.

"We have been the laughing stock of the world election after election," Walker said. "But we've still chosen not to fix this."

Separately, a federal judge in Georgia ordered state election officials to count some previously rejected ballots in that state's governor's race, where ballots are still being tallied but Republican former Secretary of State Brian Kemp has declared victory over Democrat Stacey Abrams.

This year's campaigns went down as the most expensive midterm elections in U.S. history, with some $5.25 billion spent on advertising, up 78 percent from the last midterm elections in 2014, according to a Kantar Media analysis released on Thursday. Spending was 20 percent higher than the 2016 presidential election.